(a) Field of the Invention
This invention generally relates to a device and a method which allows the accommodation of an orthopedic screw into a bone hole. More particularly, but not by way of limitation, the instant invention relates to a self adjusting system and method that includes a woven sleeve for shimming and salvaging holes for orthopedic fasteners, and for accepting and strengthening the grip of orthopedic fasteners. Additionally, the invention includes a system for delivering bone strengthening material, such as morselized bone graft material, to a location in a patient.
(b) Discussion of Known Art
The treatment of fractures frequently requires the attachment of a plate to the bone in order to ensure the correct positioning of the sections of bone that are to be fused together. To attach the plate to the bone one typically selects a plate which has pre-drilled screw hole locations. These pre-drilled screw holes are of a size that accepts a specific size of screw. Additionally, the plate also matches the size and type of bone being worked on. In order to produce the most secure attachment of the plate to the bone one should use screws which produce a close fit between the screw and the plate. The close fit between the screws and the plate results in a highly stable assembly. Unfortunately, however, the close fit that provides a stable connection provides little room for correction of imperfections in the holes drilled into the bone which should match the holes in the plate being attached to the bone. For example, slightly misplaced holes, holes which must be re-drilled, or screw holes which are stripped by over-zealous tightening of the screw, will effectively end up as being too large for ensuring the full engagement of the screw and the subsequent development of the full strength or stability which may be provided by the plate. Furthermore, depending on the brittleness of the patient's bone, the location on the bone, and the type of screw being used, or because of over-zealous tightening of the screw one may accidentally strip or damage the hole such that the full development of the strength and stability of the plate attachment is impossible to develop. Still further, bone is a non homogeneous, anisotropic material, exhibiting different strength properties depending on the direction of the stress imposed on the bone. These properties lead to bone fractures, or damaged screw holes, with seemingly random features.
To repair holes which have been damage if due to drilling, fracture, or stripping during the installation of orthopedic screws one may reposition the plate, or provide a plate with redundant holes which may be used for drilling additional screw holes in the bone for the attachment of screws to compensate for the improperly attached screws. Unfortunately, anatomic constraints and fracture configuration may limit possible screw placement sites. The original screw hole position may be the only feasible location for appropriate placement of the plate, making repair of the damaged hole the only desirable solution.
An approach at salvaging the damaged hole is the attempt to use a larger screw. However, the use of a larger screw is typically not possible due to the fact that the size of the screw, and hence the screw hole, are pre-determined by the plate being used. Of course, one may change the plate to the larger plate, for example, but this option is usually not available due to the size and location of the bone being repaired. Moreover, a larger screw may cause even greater damage to the bone being repaired. Finally, the anatomy of the location of being repaired may allow the use of a single diameter of screw. For example, the use of a large screw into the pedicle of a vertebra could break or split the pedicle.
There are several known devices designed for providing or enhancing the attachment orthopedic screws to bone. One example of these devices is shown in U.S. Pat. No. 5,084,050 to Draenert, which teaches the use of an implant that includes a sheath that holds a material that swells out once inserted in into the bone in order to provide a means for developing a firm support against the bone. This system is disadvantaged, however, due to the fact that it requires the drilling of a hole that is larger than the screw being used, and in that it does not provide an immediate secure hold against the bone. Furthermore, the Draenert device is limited in its applicability in that is primarily useful in situations where a new portion of bone is to be grown in order to support the screw. Still further, the principle operation of the Draenert device, which provides for a dowel shaped, hollow cylinder which expands to engage the surrounding bone, does not lend itself for a variety of situations, whether the situation requires the use of bone grafts or simply the accommodation of a screw where the screw hole is only slightly larger than the diameter of the screw threads.
It will become apparent that the Draenert device is almost of no use as a repair or salvaging device for situations where the hole for the screw has become damaged due to brittleness or excessive torque imposed on the screw. This is due to the fact that the damaged hole will have been originally made to correspond to the holes in the plate being attached to the bone. In other words, the damaged hole in the bone is likely to be larger than the hole through the plate; meaning that an insert such as the Draenert device would not fit through the hole in the plate. Therefore, in order to salvage the hole using the Draenert device the surgeon would have to remove the plate, adapt the hole so that it can receive the Draenert device, and then re-fasten the plate over the screw holes.
Another insert for use with bone screws in the repair of fractured bones is taught in U.S. Pat. No. 4,760,843 to Fischer et al. The Fischer patent teaches a connector with an aperture therethrough. The aperture is of a large diameter at one end and of a smaller diameter at the other end. This arrangement causes the end with the smaller diameter to expand once the bone screw is inserted into the device, gripping the inside of the hole in the bone. As can be understood from the above discussion, the use of an expanding device, such as the Fischer device, in situations where the patient's bone has already fragmented is likely to invoke even more than damage to the bone due to the fact that the hole is likely to be in brittle or soft bone. Thus, an attempt to repair a screw hole with the Fischer device is likely to result in even more damage to the hole. Still further, the Fischer device is nearly useless for the purpose of salvaging an existing hole during surgery. This is due to the fact that the stripped or damaged hole would be of a diameter that is approximately equal to the diameter of the hole through the plate; meaning that to salvage the hole, the surgeon would have to select the appropriate size Fischer connector and select a new screw that would cooperate with the Fischer connector. This is likely to produce a loose connection since the largest diameter of the plug sleeve portion of the device will necessarily be approximately the same size as the hole in the plate, preventing proper gripping of the bone immediately below the plate. Finally, an expanding device may fracture or "blow out" bone in certain anatomical area, such as the tube-like confines of the vertebral pedicles, and may increase the risk of injury to surrounding anatomical structures.
The devices for use in osteosynthesis include U.S. Pat. No. 5,275,601 to Gogolewski et al. The Gogolewski patent teaches the use of a self locking resorbable screw which is made of the material with a modulus that is similar to the modulus of bone. The Gogolewski patent, however, does not teach or suggest how to solve problems associated with salvaging a hole that has been damaged while attempting to fasten the screw within the hole.
Other approaches at ensuring that a bone screw is properly fastened or seated in the bone include the approach as taught in U.S. Pat. No. 5,607,304 to Bailey et al. where a threaded connector is used in combination with an implant to support a screw. Another example is found in U.S. Pat. No. 5,425,7762 to Cohen. The Cohen patent teaches the use of a pair of sections for surgical correction of damage to the bones of the digits of the foot. These patents, however, do not teach or suggest how to salvage a screw hole once it has become damaged due to a fracture of the sides of the hole.
Also of importance is the need for a device that can accommodate a wide variety of screws, and thus can be used with a variety of screws in a variety of applications. The ability of the device to accommodate a wide variety of screws allows the device to produce consistent, reliable results. Known devices, such as the Fischer device or the Draenert device, can complicate procedures and introduce the possibility of error due to the fact that they must be matched to a particular diameter of screw. Therefore, it is possible that the surgeon may find it necessary to remove one of the Fischer devices or the Draenert device after having inserted a device which is slightly smaller than the needed device.
Thus a review of known orthopedic devices reveals a need for a device and method for salvaging damaged holes that have been drilled into a patient's bone in order to attach a screw to the bone.
Still further, a review of known devices reveals a needed for a method and a system that allows the surgeon to salvage or correct a hole that has become enlarged by erosion of the sides of the hole.
Still further, there remains a need for a system for salvaging a hole by providing self adjusting shims that accommodate to the hole in a radial manner in order to prevent bunching or folding and accumulation of the shimming material.
There remains a need for a system and method for salvaging a damaged hole for an orthopedic fastener, the system and method allowing modification of the thickness and materials used in salvaging the hole.
There remains a need for a system and method for salvaging a damaged hole for an orthopedic fastener, without having to remove plates or other devices that have been successfully attached in order to access the damaged hole.
There remains a need for a system and method that cooperates with a screw being driven into a bone and allows a surgeon to tailor the amount and kind of agents used in attachment of the screw, and thus allowing the surgeon to create an asymmetrical insert, if necessary, to accommodate the needs of the patient.